الفهرس 
Introduction
Aim of workOnly 14 pages are availabe for public view
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Abstract
Multidetector CTU (MDCTU) is rapidly gaining widespread acceptance as the imaging study of choice for complete evaluation of the urinary tract. While it has already replaced execretory urography(EU) for renal stone and renal mass imaging, many investigators also now perform MDCTU instead of EU for evaluation of the renal collecting systems, ureters, and bladder. Reliance upon axial image acquisitions, most efficiently performed with CTU. Even subtle renal collecting system abnormalities and ureteral abnormalities can be detected with MDCTU. Many of the renal abnormalities have characteristic CTU appearances. Although occasional false diagnoses may be occur, but awareness of potential pitfalls, such as ureteral kinks and prominent renal papillae, can help minimize interpretive errors. The only major concern about performing CTU exclusively rather than EU is the increased radiation dose of CTU; however, ongoing modifications in CTU techniques and CT hardware and software may soon eliminate this problem. Three-phase or two-phase split bolus studies can be successfully performed. Thin section excretory phases should be obtained using a thickness of 3 mm between 7.5 and 15 minutes after the injection of CM begins. Also coronal or sagittal reformatted images may be created that are equally effective as axial images in identifying urinary tract pathology (if images are thin enough). We have shown that a split-bolus protocol for CTU can be used successfully to evaluate for urinary tract calculi, renal abnormalities, and urothelial lesions in one simple, noninvasive examination. The split-bolus protocol reduces radiation dose to patients and results in a smaller number of images for interpretation compared with other MDCTU protocols. When compared with hybrid CT and EU strategies for the evaluation of hematuria, split-bolus CTU provides equivalent if not superior visualization of the upper urinary tracts, reduced radiation exposure.Given the significant advantages of this protocol. Split-bolus MDCTU provided at least (50%) opacification of the majority of upper urinary tract segments and had high sensitivity, specificity, and accuracy for the detection of upper urinary tract tumors. Slandered MDCTU images are obtained in the unenhanced phase (detection of calculi), nephrographic-phase (detection of renal masses) and excretory-phase (detection of urothelial lesions). The authors present their results with a protocol called split-bolus MDCTU where the unenhanced phase is followed only by a combined nephrographic and excretory phase. During split-bolus, CTU the IV injection of CM is performed in two steps. First, 40 ml is injected at 2 ml/s and after 120 second from the beginning of the first injection, the remaining 80 ml is injected.However capability of split-bolus technique for the detection of urinary calculi, renal parenchymal tumor and bladder cancers decrease as we know small bladder cancer can be missed if only excretory phase of the full bladder is obtained. Another issue that could be addressed is how the renal parenchymal masses can be adequately characterized by the combined nephrographic /excretory phase obtained with split-bolus technique. Classically, renal masses are best characterized by the combination of findings obtained without IV- CE , scans obtained in nephrographic phase (70-90 sec) and scans obtained in the excretory phase. Split bolus MDCTU may be useful for follow up patients with higher risk of develop upper tract urothelial cancer. These patients should benefit with the use of this examination, which has high accuracy for the detection of urothelial cancer and uses low dose of radiation. Also split bolus technique is helpful for whom with risk of exposure to high radiation dose such as, pediatrics, female in child bearing period and renal donors. Conclusion:- In Comparison of urinary tract distension and opacification using single-bolus 3-Phase versus split-bolus 2-phase multidetector row CT urography.The former provided better overall urinary tract distension than did split-bolus 2-phase technique. But the later detected all proven cases of tumors of the upper urinary tract, yielding high sensitivity and specificity. The split-bolus technique has the potential role to reduce both radiation dose and the number of images generated by MDCT urography